jQuery animate backgroundColor

Question

I am trying to animate a change in backgroundColor using jQuery on mouseover.

I have checked some example and I seem to have it right, it works with other properties

Answer 1

You can use jQuery UI to add this functionality. You can grab just what you need, so if you want to animate color, all you have to include is the following code. I got if from latest jQuery UI (currently 1.8.14)

/******************************************************************************/
/****************************** COLOR ANIMATIONS ******************************/
/******************************************************************************/

// override the animation for color styles
$.each(['backgroundColor', 'borderBottomColor', 'borderLeftColor',
    'borderRightColor', 'borderTopColor', 'borderColor', 'color', 'outlineColor'],
function(i, attr) {
    $.fx.step[attr] = function(fx) {
        if (!fx.colorInit) {
            fx.start = getColor(fx.elem, attr);
            fx.end = getRGB(fx.end);
            fx.colorInit = true;
        }

        fx.elem.style[attr] = 'rgb(' +
            Math.max(Math.min(parseInt((fx.pos * (fx.end[0] - fx.start[0])) + fx.start[0], 10), 255), 0) + ',' +
            Math.max(Math.min(parseInt((fx.pos * (fx.end[1] - fx.start[1])) + fx.start[1], 10), 255), 0) + ',' +
            Math.max(Math.min(parseInt((fx.pos * (fx.end[2] - fx.start[2])) + fx.start[2], 10), 255), 0) + ')';
    };
});

// Color Conversion functions from highlightFade
// By Blair Mitchelmore
// http://jquery.offput.ca/highlightFade/

// Parse strings looking for color tuples [255,255,255]
function getRGB(color) {
        var result;

        // Check if we're already dealing with an array of colors
        if ( color && color.constructor == Array && color.length == 3 )
                return color;

        // Look for rgb(num,num,num)
        if (result = /rgb\(\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*\)/.exec(color))
                return [parseInt(result[1],10), parseInt(result[2],10), parseInt(result[3],10)];

        // Look for rgb(num%,num%,num%)
        if (result = /rgb\(\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*\)/.exec(color))
                return [parseFloat(result[1])*2.55, parseFloat(result[2])*2.55, parseFloat(result[3])*2.55];

        // Look for #a0b1c2
        if (result = /#([a-fA-F0-9]{2})([a-fA-F0-9]{2})([a-fA-F0-9]{2})/.exec(color))
                return [parseInt(result[1],16), parseInt(result[2],16), parseInt(result[3],16)];

        // Look for #fff
        if (result = /#([a-fA-F0-9])([a-fA-F0-9])([a-fA-F0-9])/.exec(color))
                return [parseInt(result[1]+result[1],16), parseInt(result[2]+result[2],16), parseInt(result[3]+result[3],16)];

        // Look for rgba(0, 0, 0, 0) == transparent in Safari 3
        if (result = /rgba\(0, 0, 0, 0\)/.exec(color))
                return colors['transparent'];

        // Otherwise, we're most likely dealing with a named color
        return colors[$.trim(color).toLowerCase()];
}

function getColor(elem, attr) {
        var color;

        do {
                color = $.curCSS(elem, attr);

                // Keep going until we find an element that has color, or we hit the body
                if ( color != '' && color != 'transparent' || $.nodeName(elem, "body") )
                        break;

                attr = "backgroundColor";
        } while ( elem = elem.parentNode );

        return getRGB(color);
};

It's only 1.43kb after compressing with YUI:

$.each(["backgroundColor","borderBottomColor","borderLeftColor","borderRightColor","borderTopColor","borderColor","color","outlineColor"],function(b,a){$.fx.step[a]=function(c){if(!c.colorInit){c.start=getColor(c.elem,a);c.end=getRGB(c.end);c.colorInit=true}c.elem.style[a]="rgb("+Math.max(Math.min(parseInt((c.pos*(c.end[0]-c.start[0]))+c.start[0],10),255),0)+","+Math.max(Math.min(parseInt((c.pos*(c.end[1]-c.start[1]))+c.start[1],10),255),0)+","+Math.max(Math.min(parseInt((c.pos*(c.end[2]-c.start[2]))+c.start[2],10),255),0)+")"}});function getRGB(b){var a;if(b&&b.constructor==Array&&b.length==3){return b}if(a=/rgb\(\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*,\s*([0-9]{1,3})\s*\)/.exec(b)){return[parseInt(a[1],10),parseInt(a[2],10),parseInt(a[3],10)]}if(a=/rgb\(\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*,\s*([0-9]+(?:\.[0-9]+)?)\%\s*\)/.exec(b)){return[parseFloat(a[1])*2.55,parseFloat(a[2])*2.55,parseFloat(a[3])*2.55]}if(a=/#([a-fA-F0-9]{2})([a-fA-F0-9]{2})([a-fA-F0-9]{2})/.exec(b)){return[parseInt(a[1],16),parseInt(a[2],16),parseInt(a[3],16)]}if(a=/#([a-fA-F0-9])([a-fA-F0-9])([a-fA-F0-9])/.exec(b)){return[parseInt(a[1]+a[1],16),parseInt(a[2]+a[2],16),parseInt(a[3]+a[3],16)]}if(a=/rgba\(0, 0, 0, 0\)/.exec(b)){return colors.transparent}return colors[$.trim(b).toLowerCase()]}function getColor(c,a){var b;do{b=$.curCSS(c,a);if(b!=""&&b!="transparent"||$.nodeName(c,"body")){break}a="backgroundColor"}while(c=c.parentNode);return getRGB(b)};

You can also animate colors using CSS3 transitions but it's only supported by modern browsers.

a.test {
  color: red;
  -moz-transition-property: color;  /* FF4+ */
  -moz-transition-duration: 1s;
  -webkit-transition-property: color;  /* Saf3.2+, Chrome */
  -webkit-transition-duration: 1s;
  -o-transition-property: color;  /* Opera 10.5+ */
  -o-transition-duration: 1s;
  -ms-transition-property: color;  /* IE10? */
  -ms-transition-duration: 1s;
  transition-property: color;  /* Standard */
  transition-duration: 1s;
  }

  a.test:hover {
  color: blue;
  }

Using shorthand property:

/* shorthand notation for transition properties */
/* transition: [transition-property] [transition-duration] [transition-timing-function] [transition-delay]; */

a.test {
  color: red;
  -moz-transition: color 1s;
  -webkit-transition: color 1s;
  -o-transition: color 1s;
  -ms-transition: color 1s;
  transition: color 1s;
  }

a.test {
  color: blue;
 }

Unlike regular javascript transitions, CSS3 transitions are hardware accelerated and therefore smoother. You can use Modernizr, to find out if the browser supports CSS3 transitions, if it didn't then you can use jQuery as a fallback:

if ( !cssTransitions() ) {
    $(document).ready(function(){
        $(".test").hover(function () {
                $(this).stop().animate({ backgroundColor: "red" },500)
             }, function() {
                 $(this).stop().animate({ backgroundColor: "blue" },500)}    
             );
    }); 
}

Remember to use stop() to stop the current animation before starting a new one otherwise when you pass over the element too fast, the effect keeps blinking for a while.